1. Field of the Invention
The present invention relates to a vehicle-use generator for a vehicle such as a passenger car or a truck
2. Description of Related Art
Recently, the engine noise of a vehicle such as a passenger car or a truck is steadily reduced to meet the social demand for the reduction of vehicle noise, and also to increase merchantability of the vehicle. However, reducing the engine noise tends to make the noises of auxiliaries rotating at relatively high speeds which are mounted on the same vehicle, especially a vehicle-use generator, more harsh and conspicuous.
There have been proposed various techniques for reducing the noise of a vehicle-use generator, while improving the self-cooling capability of the vehicle-use generator by making changes to the shape around cooling air outlet windows formed in a housing of the generator. For example, Japanese Patent Application Laid-open No. 2000-69714 discloses smoothing a cooling air flow by streamlining ribs made so as to form cooling air outlet windows, to thereby reduce the drag force of the cooling air flow. Japanese Patent Application Laid-open No. 7-79543 discloses reducing the drag force of a cooling air flow by elaborating on the inclination of ribs around support members of a housing of a vehicle-use generator.
However, the structures disclosed in the above described patent documents have a problem in that the fan noise of the vehicle-use generator is not reduced much, because the reduction of the drag force of the cooling air flow around the ribs or the support members of the housing causes the cooling air flow to increase that much. Moreover, although the fan noise may contain a specific order component which is harsh to hear depending on a distance between adjacent ribs or adjacent cooling air outlet windows when they are evenly spaced in a circumferential direction, no consideration on this is given in these documents.